You can only directly add plugins from the plugin list to your Minehut server, however, you can request plugins to be added to the plugin list on the current forum's category that you're in.
I'm sure it would be allowed on the anarchy server, however it may be punishable for doing it on the other server. I'm not sure what Minehut considers community disruption.
Most (if not all) skyblock plugins allow you to right click the obsidian with a bucket to turn it back into lava if this happens; rendering this pointless.